Cell adhesions, cell junctions and extracellular structures Flashcards
Epithelium
sheets of cells that are
polarized, with discrete functional
domains at opposite ends (apical and
basal) of the cells.
Connective tissue
more loosely
organized, in which cells are attached
to each other, a rigid scaffold, or both
Cell-Cell Junctions
Specialized structures where
two cells come together are
called cell-cell junctions
Type of animal cell junctions
- Adhesive junctions
- Tight junctions
- Gap junctions
plant junctions
Plant cells have special structures
called plasmodesmata
cell table
Adhesive Junction
Link adjoining cells
* Adhesion proteins are key
* Some need a linker protein
* Cadherins
* Are dynamic
Types of adhesive junctions interactions
Homophilic interactions: same
* Heterophilic interactions: different
Cadherin characterisation
“Repeats” in their extracellular domain
➢ A transmembrane domain.
➢ Varying cytosolic ends.
E-cadherins
E-cadherins are found on epithelial cells
P-cadherins
P-cadherins in placenta (and other tissues)
Cadherin function
- The amount and type of cadherins on cell surfaces help
segregate cells into specific tissues. - Cadherin expression is essential for organization of cells during
development
Desmosomes
Provide a tissue with structural
integrity
* The desmosomal cadherins are
called desmocollins and
desmogleins.
* Linker protein = planktoglobin
cell-cell adhesions for cellular events
- Lectins
- Cell adhesion molecules
(CAMs) - Selectins – e.g. Leukocyte
adhesion during
inflammation.
insert
Tight Junctions
Seal the gap between
adjacent epithelial
cells